A standard construction for thermostatic switches involves aligned contacts mounted on flexible strip members, at least one of the strips, or an adjacent piece, being formed of a usual bimetal for actuation of the device at a predetermined temperature. If one of the flexible arms is not formed of a bimetallic material, then a further bimetallic member must be formed which is in alignment with the flexible metal strips on which the aligned contacts are formed.
In many cases it is desirable to press fit this stack of operative members into a metallic casing. The metallic casing may form a contact for the device, or the device, even with the metal case, may be of the dead case type. Generally speaking, whether the case is a dead case or a live case is determined by the positioning of the flexible strip members in the stack and within the case.
One construction which allows the insertion of the operative members of the thermostatic switch stack into the metallic case is illustrated in U.S. Pat. No. 3,223,809, Wehl, assigned to the same assignee as the present invention. This patent describes and claims a U shaped, upwardly open block formed of an electrically insulating material, preferably porcelain. The operative portions of the thermostatic switch, including the flexible arms in which the contacts are mounted, the bimetallic member, and adjustment means, are mounted within, or adjacent to, this U shaped insulator.
A difficulty is encountered with this U shaped insulator, either with a dead or live case thermostatic switch, when operative members of the device must be placed adjacent both the top and the bottom of the case, but must be insulated from each other within the stack. For example, in copending application Ser. No. 234,242--Givler, now U.S. Pat. No. 4,335,368, issued June 15, 1982, assigned to the same assignee as the present invention, a dead case thermostat is described where the bimetallic member is placed on the bottom of the stack and is electrically insulated from the flexible arms. Because of this required construction, either the U shaped insulator of U.S. Pat. No. 3,223,809 cannot be adequately used, additional steps are required for assembly, or additional pieces are required for formation of an operative device.